1. Field of the Invention
The present invention relates to a technique for printing images by ejecting ink drops.
2. Description of the Related Art
Ink-jet printers are widely used as computer output devices. Most of the ink-jet printers are color printers capable of printing in color.
A color printer needs to have good image quality and a high printing speed. The image quality of printed color images can be dramatically improved by the use of light cyan and magenta inks. Printing can be speeded up by increasing the number of nozzles for each ink. It is, however, necessary to increase the number of nozzles for all the inks in order to accelerate printing when images are printed in color, so it is sometimes difficult to accelerate printing in this manner.
An object of the present invention is to provide a technique for improving printing speed during color printing.
In order to attain at least part of the above and other related objects of the present invention, there is provided a printing device for printing images on a printing medium during main scanning. The printing device comprises: a print head having a plurality of nozzle arrays for ejecting multiple types of ink, and a plurality of ejection drive elements for causing ink drops to be ejected from nozzles of the plurality of nozzle arrays. The printing device further comprises: a main scan drive unit for performing main scans by causing the printing medium and/or the print head to move; a sub-scan drive unit for performing sub-scans by causing the printing medium and/or the print head to move; a head drive unit for sending drive signals to the ejection drive elements in accordance with given print signals; and a control unit for controlling each of the above units. The print head comprises N nozzle arrays for ejecting N types of identically hued inks, respectively, for at least for one hue, where N is an integer of 2 or greater. The identically hued inks are inks that have substantially a same hue but mutually different densities. The control unit has a specific print mode in which tone reproduction using the N types of identically hued inks is performed such that (i) a print area is divided into pixel blocks each consisting of N pixels, and (ii) the N pixels in each pixel block are assigned to ejection positions of the N types of identically hued inks, respectively.
The print head may have N nozzle arrays for ejecting the N types of identically hued inks for cyan and magenta. The control unit may operate in the specific print mode such that (iii) tone reproduction for cyan and magenta is performed using the N types of identically hued inks in each pixel block for each of the cyan and magenta; and (iv) tone reproduction for at least one of yellow and gray is performed by forming large dots of corresponding ink across a plurality of pixels.
The present invention can be implemented in various embodiments, such as a printing method and a printing device, a print control method and a print control device, a computer program for implementing the functions of these methods or devices, a recording medium having the computer program recorded thereon, and data signals embodied in a carrier wave containing the computer program.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with the accompanying drawings.